OPTICAL AND X-RAY STUDIES OF THIN MIXED-CRYSTALS OF NACL-TYPED RBI AND CSCL-TYPED CSI

Thin Rbl-xCsxI mixed crystals have-been grown from the melt in a very small gap formed in between a pair of quartz plates and reflection spe ctra were measured in the uv-light region at low temperature. Continuo us spectral changes of the exciton bands with the;composition x sugges t strongly the formation of extended solid solution both in the RbI-ri ch (0.0 less than or equal to x less than or equal to 0.4) and CsI-ric h (0.7 less than or equal to x less than or equal to 1.0) regions. The formation was confirmed by x-ray diffraction, and the compositional c hange of the-lattice constant was determined. These results are in con trast to the eutectic:type phase relation with only a limited solid so lubility observed in the built state of the RbI-CsI binary system. (C) 1998 American Institute of Physics.